Data from: Investigating population differentiation in a major African agricultural pest: evidence from geometric morphometrics and connectivity suggests high invasion potential

The distribution, spatial pattern and population dynamics of a species can be influenced by differences in the environment across its range. Spatial variation in climatic conditions can cause local populations to undergo disruptive selection and ultimately result in local adaptation. However, local adaptation can be constrained by gene flow and may favour resident individuals over migrants—both are factors critical to the assessment of invasion potential. The Natal fruit fly (Ceratitis rosa) is a major agricultural pest in Africa with a history of island invasions, although its range is largely restricted to south east Africa. Across Africa, C. rosa is genetically structured into two clusters (R1 and R2), with these clusters occurring sympatrically in the north of South Africa. The spatial distribution of these genotypic clusters remains unexamined despite their importance for understanding the pest's invasion potential. Here, C. rosa, sampled from 22 South African locations, were genotyped at 11 polymorphic microsatellite loci and assessed morphologically using geometric morphometric wing shape analyses to investigate patterns of population structure and determine connectedness of pest-occupied sites. Our results show little to no intraspecific (population) differentiation, high population connectivity, high effective population sizes and only one morphological type (R2) within South Africa. The absence of the R1 morphotype at sites where it was previously found may be a consequence of differences in thermal niches of the two morphotypes. Overall, our results suggest high invasion potential of this species, that area-wide pest management should be undertaken on a country-wide scale, and that border control is critical to preventing further invasions.

物种的分布、空间格局及种群动态，可受其分布范围内环境异质性的影响。气候条件的空间异质性可导致局域种群经历分裂选择（disruptive selection），最终引发本地适应（local adaptation）。然而，基因流（gene flow）会限制本地适应的进程，且本地适应可能更青睐本地个体而非迁入个体——这两类因素均对入侵潜力（invasion potential）评估至关重要。
纳塔尔实蝇（Ceratitis rosa）是非洲主要农业害虫，虽有入侵岛屿的记录，但其分布范围主要局限于非洲东南部。
在非洲全域范围内，该实蝇的遗传结构（genetic structure）可划分为两个类群（R1与R2），这两个类群在南非北部呈同域分布状态。尽管这两个遗传型类群对理解该害虫的入侵潜力具有重要意义，但其空间分布格局至今尚未被系统研究。
本研究对采自南非22个采样点的纳塔尔实蝇样本，通过11个多态微卫星位点（microsatellite loci）进行基因分型（genotyping），并利用翅形几何形态测量（geometric morphometric）分析开展形态学鉴定，以探究其种群结构格局，并明确该害虫侵染位点间的连通性（connectedness）。
研究结果显示，南非境内的纳塔尔实蝇几乎不存在种内（种群间）分化，种群连通性高，有效种群规模（effective population sizes）大，且仅存在一种形态型（morphotype，R2）。此前曾记录有R1形态型的采样点如今未再检出该类群，这一现象可能源于两个形态型间的热生态位（thermal niches）差异。
综合来看，本研究结果表明该物种具有极高的入侵潜力，因此需在全国范围内实施全域性害虫综合治理，且边境管控对阻止后续入侵事件至关重要。